Emit all string fields on Rust-upb regardless of ctype set.

As ctype only affects cpp implementation, these fields necessarily already work the same as any other string field.

PiperOrigin-RevId: 646156640

rust/test/BUILD

@@ -39,7 +39,10 @@ rust_cc_proto_library(
 rust_upb_proto_library(
     name = "unittest_proto3_upb_rust_proto",
     testonly = True,
-    visibility = ["//rust/test/shared:__subpackages__"],
+    visibility = [
+        "//rust/test/shared:__subpackages__",
+        "//rust/test/upb:__subpackages__",
+    ],
     deps = [UNITTEST_PROTO3_TARGET],
 )
 

rust/test/upb/BUILD

@@ -10,3 +10,19 @@
 # * `rust_upb_proto_library` instead of `rust_proto_library`.
 # * `//rust:protobuf_upb_export` instead of
 #   `//rust:protobuf`.
+
+load("@rules_rust//rust:defs.bzl", "rust_test")
+
+# TODO: Enable this for the cpp kernel and move these tests to shared.
+rust_test(
+    name = "string_ctypes_test_upb_test",
+    srcs = ["string_ctypes_test.rs"],
+    aliases = {
+        "//rust:protobuf_upb_export": "protobuf",
+    },
+    deps = [
+        "//rust:protobuf_upb_export",
+        "//rust/test:unittest_proto3_upb_rust_proto",
+        "@crate_index//:googletest",
+    ],
+)

rust/test/upb/string_ctypes_test.rs

@@ -0,0 +1,35 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google LLC.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+use googletest::prelude::*;
+use unittest_proto3_rust_proto::TestAllTypes;
+
+#[test]
+fn test_stringpiece_repeated() {
+    let mut msg = TestAllTypes::new();
+    assert_that!(msg.repeated_string_piece().len(), eq(0));
+    msg.repeated_string_piece_mut().push("hello".into());
+    assert_that!(msg.repeated_string_piece().len(), eq(1));
+    assert_that!(msg.repeated_string_piece().get(0), some(eq("hello")));
+}
+
+#[test]
+fn test_cord() {
+    let mut msg = TestAllTypes::new();
+    assert_that!(msg.optional_cord(), eq(""));
+    msg.set_optional_cord("hello");
+    assert_that!(msg.optional_cord(), eq("hello"));
+}
+
+#[test]
+fn test_cord_repeated() {
+    let mut msg = TestAllTypes::new();
+    assert_that!(msg.repeated_cord().len(), eq(0));
+    msg.repeated_cord_mut().push("hello".into());
+    assert_that!(msg.repeated_cord().len(), eq(1));
+    assert_that!(msg.repeated_cord().get(0), some(eq("hello")));
+}

src/google/protobuf/compiler/rust/accessors/accessors.cc

@@ -27,10 +27,11 @@ namespace {
 std::unique_ptr<AccessorGenerator> AccessorGeneratorFor(
     Context& ctx, const FieldDescriptor& field) {
   // TODO: We do not support ctype=CORD fields or repeated
-  // ctype=STRING_PIECE fields.
+  // ctype=STRING_PIECE fields on cpp kernel yet (upb doesn't care about ctype).
   auto ctype = field.options().ctype();
-  if (ctype == FieldOptions::CORD ||
+  if (ctx.is_cpp() &&
-      (ctype == FieldOptions::STRING_PIECE && field.is_repeated())) {
+      (ctype == FieldOptions::CORD ||
+       (ctype == FieldOptions::STRING_PIECE && field.is_repeated()))) {
     return std::make_unique<UnsupportedField>(
         "fields has an unsupported ctype");
   }